I'm in need of "runtime decorators". That is, a class whose constructor is to take an instance of either the base class or a separate "runtime decorator" and add functionality to it. I don't know ahead of time what the type of the object will be.
Here's an extremely contrived example of what I want to do (this strategy makes sense in the actual problem domain).

I need the flexibility to be able to chain decorators together and still have available to methods added from the decorator before it.
Is there a name for what I'm trying to do and can this be done easily without the help of a module or is there a module which can help me achieve this?

UPDATE:
This is getting closer to what I want, but it still adds to the class rather than the object

I should have mentioned that. It's no problem in my case, because I know none of the plugins will override each other (and no code wants to use an unmodified MyApp object), but Moose traits are more general and applicable.